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Seasonal succession,standing crop and determinants of primary productivity of the phytoplankton of Ministik Lake,Alberta, Canada
Authors:Michael Hickman
Institution:(1) Department of Botany, University of Alberta, T6G 2E9 Edmonton, Alberta
Abstract:Ministik Lake (longitude 113°01prime; latitude 53°21prime), a well-mixed, shallow (mean depth 1.83 m), eutrophic lake is characterized by eutrophic chlorococcalean and cyanophycean phytoplankton associations, and little change in standing crop size with increasing depth. Standing crops and primary productivity are low during the winter but pronounced spring and late summer/early autumn maxima occur. Mean yearly areal standing crop (sumB) and primary productivity (sumA) were 199.2 mg m–2 chlorophyll a and 319.5 mg C hr–1 m–2 respectively. Annual productivity was estimated at 1399,6 g C m–2yr–1. The mean increase in the extinction coefficient (isin) per unit increase in standing crop (B) was 0.03 In units m–1. High non-algal light attenuation (isinq) occurred averaging 46% which prevented the ratio Bisin from attaining more than 74.2% of the theoretical maximum except once when selfshading occurred. Insignificant relationships existed between B (mg m–3 chlorophyll a) and Amax (mg C hr–1 m–3), sumA and sumB and sumA and B. Close correlations existed between sumA and Amax/isin and sumA and I0 (W m–2). The depth of the euphotic zone (Zeu) varied between 0.6 and 2.0 m; the average relationship between zeu and isin was zeu = 3.78/te, and the mean standing crop in the euphotic zone represented 58.3% of the theoritical maximum. The high isinq values made the model of Talling (1957) inapplicable to this lake. The Q10 value for the lake was 1.20. emptyvmax (mg C chlorophyll a –1 hr–1) was closely related to both temperature and irradiance, and depressed by high pH values.Growth of the cyanophycean algae was correlated with temperature, chlorophycean algae with phosphate-phosphorus and temperature and the diatoms with dissolved silica and phosphate-phosphorus, but only in the case of Chaetoceros elmorii did any nutrient appear limiting. Indirect evidence that free CO2 limited photosynthetic rates is provided by the emptyvmax:pH relationship.
Keywords:Phytoplankton  seasonal succession  standing crop  determinants of primary productivity
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